An iscosceles triangle is triangle that has same length in 2 of the sides, it also has 2 angles in the same size.
The first option.
If an angle is 30°, then one of other angle is 30° too. The sum of interior angles in triangle is 180°. Now find the third angle.
∠1 + ∠2 + ∠3 = 180°
30° + 30° + ∠3 = 180°
60° + ∠3 = 180°
∠3 = 120°
The other angles are 30° and 120°
The second option.
If an angle is 30°, then the other two angles are same size. The sum of interior angles in triangle is 180°. Now find the second and third angles.
∠1 + ∠2 + ∠3 = 180°
∠1 + 2 × ∠2 = 180°
30° + 2 × ∠2 = 180°
2 × ∠2 = 150°
∠2 = 75°
The other angles are both 75°
SUMMARY
The first option: 30° and 120°
The second option: 75° and 75°
